Lubricant compositions



United States Patent O 3,210,276 LUBRICANT COMPOSITIONS Edwin L. De Young, Milwaukee,'Wis., and Roger W.

Watson, Highland, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Filed Jan. 16, I962, Ser. No. 167,219 Claims. '(Cl. 252-463) This invention relates to certain silicon-containing com positions useful as anti-wear additives in lubricants normally tending to cause excessive wear of silver bearings.

Many hydrocarbon lubricant oils are compounded with various sulfur compounds which act as oxidation or corrosion inhibitors. Sulfur compounds, however, promote excessive wear in silver and silver-containing bearings and bushings.

It has now been discovered that such excessive wear of silver bearings and the like may be inhibited substantially by incorporating into hydrocarbon lubricant oils which tend to exhibit excessive silver wear a minor amount of a compound having the structure (RCO Si in which the Rs are the same or different alkyl groups having up to about 19 carbon atoms per group.

Hydrocarbon lubricant oils which may be improved with respect to their silver wear characteristics according to the invention may be any of the natural or synthetic hydrocarbon oils of suitable viscosity range, e.g., from about 20 SSU viscosity at 100 F. to about 3,000 SSU at 210 F. These may be derived from natural, i.e., mineral, sources such as petroleum oils, or may be composed in whole or in part of synthetic hydrocarbon, as for example the polybutenes. The oils may contain any of the ingredients normally incorporated for the purpose of improving detergency, oxidation resistance, lubricity, extreme pressure characteristics, rust inhibition, etc. Ordinarily, it is considered that sulfur-containing materials tend to be most deleterious from the standpoint of silver wear, and accordingly it is with sulfur-containing hydrocarbon oils that the inventive additives have their most attractive utility.

By way of illustration, sulfur-containing additives normally present in lubricant oils include the sulfurized terpenes, sulfurized tall oil, octyl polysulfide, various reaction products of phosphorus pentasulfide with olefinic hydrocarbons, metal sulfonates, sulfochlorinated olefins, etc.

The inhibitors described herein may be prepared by reacting the corresponding fatty acid with silicon tetrachloride or, more desirably, with silicon disulfide following the procedure of Malatesta, Gazz. Chim. Ital., 78, 753-63 (1948); Chemical Abstracts, 43, 4630 (1949). According to either of these techniques, a silicon reactant is contacted with the corresponding fatty acid under anhydrous conditions and at a temperature sufiicient to cause reaction. Reaction may be terminated when gas evolution (hydrogen chloride or hydogen sulfide, depending upon the silicon reactant) ceases.

Suitable fatty acids for use in accordance herewith in clude the following, either alone or in admixture with each other: formic, acetic, propionic, n-butyric, isobutyric, n-valeric, isovaleric, methylethylacetic, trimethylacetic, caproic, heptoic, caprylic, pelargonic, capric, undecylic, lauric, tridecylic, myristic, pentadecylic, palmitic, margaric, stearic, nondecylic, arachidic. Optimally, the fatty acid or acids is selected to provide an R in the previouslygiven formula of from 2 to 12 carbon atoms so that an optimum balance of oil solubility and eflicacy can be obtained, and so that the product is more resistant to hydrolysis in use.

The inventive additive may be incorporated into hydrocarbon lubricant oils in a wide range of concentrations, with the optimum concentration depending upon the initial. wear characteristics-of theoil, .the nature of wear- .promotingadditives inwthe oil, and :the extent of inhibitionidesired. In general,concentrationsof as little as 0.05 wei'ghtpercent, or even less, .upto as'much.as:3 percent by weight, or even more, will provide suitable inhibition. However, for any particular lubricant composition it is a simple matterytozconduct'ntests whichswill provide a quantitativeor semi-quantitative,indication of the requisite Example I This example illustrates the preparation and testing of an additive prepared from caproic acid.

To' 25 grams (0.2 mol) of technical caproic acid is added 4.6 grams (0.05 mol) of silicon disulfide. The mixture is heated for 6 hours at 200 C., after which no more evolution of hydrogen sulfide is observed. Excess acid is then removed by vacuum distillation. The resultant product (R has 5 carbon atoms) analyzes at 9.7 weight percent silicon.

The product is tested for its elfectiveness as a silver wear inhibitor by incorporating it into a lubricant oil composed of 73 viscosity index mineral base oil, 2.8 Weight percent detergent (barium neutralized and hydrolyzed reaction product of phosphorus pentasulfide and a hydrocarbon), 1.0 percent calcium phenate, and 0.2 percent sulfurized terpene.

The above lubricant composition, in the absence of any of the present inhibitor, exhibits a weight loss of 275 milligrams. However, with only 0.5 percent inhibitor, the weight loss is 34.2 and 40.2 milligrams in duplicate tests.

Example 11 Example I is repeated, except that an equal molar amount of acetic acid is employed for the preparation. At a concentration of 0.05 weight percent, excellent inhibition of silver wear is achieved.

Example III Example II is repeated with isobutyric, capric, myristic, stearic, and arachidic acids. At concentrations approximating 0.05 weight percent, satisfactory inhibition is achieved.

Thus it is evident that there has been provided, in accordance with the invention, an outstanding additive for improving the silver wear characteristics of hydrocarbon lubricant oils which normally tend to cause such wear. While the invention has been described in conjunction with specific embodiments thereof, particularly in connection with organic sulfur containing mineral lubricants, it is evident that many alternatives, modifications, and variations of the invention will occur to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.

We claim:

1. A hydrocarbon lubricating oil containing a sulfurcontaining additive normally causing excessive silver wear and a minor amount sufiicient to inhibit such wear of a compound having the formula (RCOO) Si wherein R is C1 19 alkyl.

2. The composition of claim 1 wherein R is C alkyl.

3 4 3. The composition of claim 1 wherein each R is C 2,634,285 4/53 Rust et al. 252-495 X alkyL- 2,703,784 3/55 Fields 25246.6 X

4. Composition of claim 1 in which said amount is OTHER REFERENCES within the range of about 0.05 to 3.0 weight percent. I

A mineral lubricating oil containing a lf i d 5 Post, The Chemistry of the Aliphatic Orthoesters,1943,

terpene normally causing excessive silver wear and from P about 0.05 to about 3.0 weight percent of a compound having the formula (RCOOhSi wherein R is C alkyl. DANIEL WYMAN Primary Exammer- ALPHONSO D. SULLIVAN, Examiner. References Cited by the Examiner V UNITED STATES PATENTS 2,405,988 8/46 Barry 252-496 X 

1. A HYDROCARBON LUBIRCATING OIL CONTAINING A SULFURCONTAINING ADDITIVE NORMALLY CAUSING EXCESSIVE SILVER WEAR AND A MINOR AMOUNT SUFFICIENT TO INHIBIT SUCH WEAR OF A COMPOUND HAVING THE FORMULA (RCOO)4SI WHEREIN R IS C1-19 ALKYL. 